ACTG 179 is a Phase I/II, comparative, randomized, open-label, two-dose study of dapsone for PCP prophylaxis in HIV-infected infants and children 1 month to 12 years of age who are intolerant to trimethoprim-sulfamethoxazole. Children will be randomized to receive dapsone 1 mg/kg p.o. once daily or dapsone 4 mg/kg p.o. once weekly. Endpoints to be monitored include hematologic and dermatologic toxicity to dapsone.